Process for producing armor plates



Aug. 6, 1935. J, J STQNE 2,010,650

PROCESS FOR PRODUCING ARMOR PLATES Filed Sept. 3, 1931 2 Sheets-Sheet l Aug. 6, 1935. J STONE 2,010,650

PROCESS FOR PRODUCING ARMOR PLATES Filed Sept. 3, 1931 2 Sheets-Sheet 2 Patented Aug. 6, 1935 UNITED STATES PATENT orrlcs PROCESS FOR PRODUCING ARMOR PLATES John J. Stone, Bethlehem, Pa., assignor to Bethlehem Steel Company, a corporation of Pennsylvania Application'september 3, 1931, Serial No. 560,929

2 Claims.

A, h properties throughout the metal. To this end I 10'- use a corrugated ingot and forge two plates therefrom-the major portion of each plate being taken from the external zones of the ingot.

As is well known in the art, a selective freezing action takes place during the solidification of an ingot whereby the metal which solidifies first near the ingot surface contains more iron and less of the minor constituents of the steel (carbon, manganese phosphorus, sulphur, etc.) than the average composition of the liquid metal. As freezing progresses toward the center of the ingot, the proportion of minor constituents in creases uritil there is produced a marked zone of segregation at the core. This central core is also apt to contain voids due to shrinkage of the surrounding metal unless skill is used in so designing the ingot and controlling the pouring process that the voids are filled by molten metal fed from the top. Since solidification proceeds from the bottom of the ingot as well as from the sides, there is a tendency for the upper portion of the core to be most seriously affected by segregation and, in spite of the best ingot design and pouring practice, there is always a conical shaped zone at the top of the core containing porous metal and known as the pipe. In order to completely remove the pipe it is common practice to discard from the top of a largeingot as much as 30% or more of the ingot weight.

The approximate location and shape of the pipe in various ingots-together with the consecutive steps in my improved forging processare illustrated in the drawings which form part of this specification.

Fig. 1 represents an armor plate ingot;

Fig. 2 shows the ingot of 1 in longitudinal section;

Fig. 3 shows a corrugated ingot such as used in my improved process for making armor plate;

Fig. 4 is a longitudinal section of the ingot of Fig. 3; and

Figs. 5, 6, 7, 8, and 9 illustrate successive stages in the forging of the ingot of Fig. 3 by my process.

In producing fiat forgings such as armor plate rectangular ingots have been almost universally used heretofore. In fact a particular type of (Cl. ZED-160.4)

rectangular ingot has come to be known as an armor plate ingot. The characteristic proportions of this ingot are a height or length approximately equal to its width, and a thickness equal to one fourth or one fifth of same. The corners are only slightly rounded. The advantages of this type of ingot for producing armor plate reside in the relative ease with which it may be handled under the forging press and in thefact that the segregated core is spread out fairly uniformly over a considerable portion of the width of the ingot. The general shape of'an ingot of this type and the location and extent of the pipe and zone of segregation therein are illustrated in Figs. 1 and 2. While the presence of the segregated zone is undesirable it has been found less deleterious to have it spread out in this way thanto have it concentrated along a definite line in the finished plate-as would be the case for example if a square ingot were used.

Two major disadvantages of the armor plate type of ingot are its tendency to form surface cracks in cooling or subsequent forging and the practical impossibility of removing segregated metal from the body of the ingot. A further disadvantage inherent in the process of making plate from rectangular ingots is the fact that a large part of the mechanical work of forging only produces elongation of the ingot crystals parallel to the long dimension of the finished plate. The result is that the physical properties of the plate as determined on transverse specimens are markedly inferior to those on longitudinal specimens. While this is true of many steel products--particularly rolled sections-and is taken into account in designing, it is obviously undesirable.

It has long been recognized that corrugated ingots are less apt to develop cracks in cooling and forging than rectangular ingots due to the more favorable arrangement of crystals adjacent their surfaces. Fig. 3 illustrates an ingot of this type and Fig. 4 which is a longitudinal section of the ingot of Fig. 3 shows the location of the segregated zone therein. Figures 5, 6, 7, 8, and 9 illustrate successive stages in my improved forging process as applied to plates. Fig. 5 shows the ingot of Fig. 3 after being rounded up and after the removal of discard metal from both ends. In Fig. 6 the cylindrical faggot of Fig. 5 has been spread and edged to a rectangular shape; Fig. 7 shows its condition after further transverse forging. In Fig. 8 the slab has been cut in two parallel to the axis of the ingot. Fig. 9 shows the plates forged longitudinally to finished dimensions plus trimming allowance.

It is obvious that the transverse forging illustrated by Figs. 6 and 7, followed by the longitudinal forging shown in Figs. 8 and 9 has a tendency to equalize the mechanical work applied to the ingot structure in these directions and that the physical properties of the resulting plate will be more nearly uniform with respect to the directions in which they are determined. The most important feature of my process', ho'wever, is the forging of two plates from a single ingotthe parting out being made through the axis of the ingot. If it were otherwise desirable to forge a single plate from a corrugated ingot the presence of a concentrated zone of segregated metal along the longitudinal axis of the plate would make the product undesirable; but by making the plates from metal which is largely outside this zone and by eliminating the major portion thereof in the trimming allowance between plates I obtain the advantages of great reductionin cross section and of forging intwo directions without the detrimental effect of concentrated segregation.

I have heretofore referred to the production of two plates from a single ingot but it will be readilyunclerstood that any even number of plates mayjbe produced from an ingot without losing the advantages set forth. In the manufacture o'farmor plate it isconvenient to produce plates pairs since. two identical plates of each size and shape are ordinarily required for a shipone starboard and one port. It is my preferred practice tojcast a corrugated ingot of s'ufiicient size to produce two large plates or four small'ones. As a matter of convenience/I prefer to cut the cross forged slab longitudinally while hot. When the'lforging operations on the individual slabs are-completed the finished dimensions of the plate are then laid out on the slab so that the maximum trimming allowance is on the side adjacent the parting cut. This permits removing the major portion of the segregated zone when the plates are machined to finished size. However, it may be desirable in certain cases to cut a strip either hot or cold from the center of the cross forged slab in order to more completely remove the segregated zone. The heavy sections and the variety of sizes and shapes of armor plates ordinarily preclude rolling as a manufacturing process. Since I have confined this illustration of my process to armor plate, I have consistently referred to forging as the method of working or shaping the metal. The advantages of myprocess however, may also be secured in, the manufacture of lighter and more uniform steel articles byrolling. These variations in procedure come Within the scope of my invention.

' Having thus described my invention what I claim as new and desire to secure by Letters Patent is: V 'v 1. In the production of armor plate the steps of forging a corrugated ingot of substantially circular cross section transversely to its major axis,severing the resulting slab through said axis and forging the resulting portions parallel to said axis.

2. In the'production of armor plate the steps of forging a corrugated'ingotof substantially circular cross section transversely to its major axis, severing the resulting slab through said axis, forging the resulting portionsparallel to said axis, andremoving a portion of the metal from the edges of said portions adjacent the parting cut.

JOHN J. STONE. 

